In recent years, a tunnel FET (TFET) has been vigorously studied to achieve higher performance and lower power consumption compared to a MOSFET. In the tunnel FET, since conductivity types of source and drain regions differ from each other, bipolarity of the tunnel FET in which the FET is turned on regardless of whether a gate voltage is positive or negative raises a problem. This brings about an increase in off-state current and an increase in variation of characteristics of the tunnel FET. Although several solutions for suppressing the off-state current are proposed, many of them bring about harmful effects such as degradation in on-state current and reduction of sub-threshold swing (SS). Those effects become factors that hinder the reduction in power consumption of the tunnel FET.